For an apparatus that uses a motor, as in a hybrid vehicle and an electric vehicle, a power converter is used to save energy. For the power converter, a power semiconductor module that includes power semiconductor elements, such as IGBT (Insulated Gate Bipolar Transistor), is widely used. The power semiconductor elements heat up when controlling heavy current, hence in order to cool the power semiconductor elements, a water cooling type power semiconductor module structure, in which a plurality of fins is integrated into a heat radiation board, is used.
Such a power semiconductor module has, for example, an insulated wiring board which includes: a ceramic board having an insulate thin plate; a metal circuit wiring layer which is directly bonded or brazed to one surface of the board; and a metal layer which is directly bonded or brazed almost to the entire surface of the other side. Electric semiconductor elements are soldered to a part of the surface of the metal circuit wiring layer, and a heat radiation board is soldered to the metal layer formed on the rear surface of the insulated wiring board. Further, a known power semiconductor module has a structure that includes, on the opposite side (lower side surface) of the heat radiation board: a plurality of fins which is integrated and bonded at predetermined intervals; and a container that surrounds all the fins with an opening which allows cooling water to easily flow through the spaces formed among the plurality of fins (Patent Document 1). The power semiconductor module has a structure where a separate heat radiation board for holding the fins is not inserted, or a structure where heat radiation grease does not exist between the heat radiation board and the fins. In other words, the insulated wiring board that mounts the semiconductor elements is directly bonded to the heat radiation board, which is integrated with the fins, whereby the thermal resistance from the semiconductor elements to the heat radiation board is decreased, and heat radiation and reliability of the product are improved. For this, a heat radiation board is formed from a material of which main component is aluminum or copper.
Other documents disclose techniques regarding a semiconductor element cooling radiator which reduces stress due to the thermal expansion difference among members forming the semiconductor module, and miniaturizes and simplifies the semiconductor module by decreasing a number of components (Patent Documents 2, 3).
Another document discloses a technique regarding a semiconductor device where the warpage of the heat sink is suppressed, and a warpage suppression plate can be easily brazed to the heat sink (Patent Document 4).
Patent Document 1: Japanese Patent Application Publication No. 2007-36094
Patent Document 2: Japanese Patent Application Publication No. 2007-173301
Patent Document 3: Japanese Patent Application Publication No. 2008-270297
Patent Document 4: Japanese Patent Application Publication No. 2010-182831